"I'm not overly concerned about the market volatility," Mnuchin said on Capitol Hill Tuesday, as he momentarily checked his phone to relay to lawmakers that the Dow was "now up 187 points."

The global market selloff -- the largest decline in the last six-and-half years -- was portrayed by House Republicans as an overdue "technical correction" that didn't signal underlying weakness in the U.S. economy.

"How ironic, but totally predictable, that equity markets would now swoon over the prospects of higher interest rates and possible inflation associated with a breakout of economic growth," said Rep. Jeb Hensarling, the Republican chairman of the House Financial Services Committee. "Artificially low interest rates may have benefited some on Wall Street but they haven't been particularly helpful to Main Street."

The U.S. economy is getting stronger. Economic growth is at 3% -- again. The unemployment rate is at a 17-year low. And Americans wages are finally on the rise.

"I think the fundamentals are quite strong," Mnuchin said.

Ahead of Tuesday's hearing, Mnuchin said he spoke to market players to ensure that traders and other companies that keep the markets running were ready for action. "I'm happy to report that I have the green lights," he said.

He added, "We continue to believe in the long-term impact on the stock market."